Is your kitchen missing a cutting board?
In the matter of fact it is missing a few. So far I found several good uses for it. Here is cutting board machined in donuts and used for inside of the aluminum feet for the X600, so that prevents floor scratching. (located at the end of the table on the right) And the shot of finished feet.
Cutting board is really cool and useful item.
Attachments
Thank you!
For the very short time I was running this amp, it is noticable that, when it comes to adjustment of the DC offset (each positive output to ground) it takes a long time to settle, and than it is very sensitive to temperature changes. Even blowing on CCS - SJ74 version, will immediately change set values. As you could see in the picture I do not have it in the case, it is out in the open and obviously it is affected by outside temperature changes. Even with the small draft it will swag in one or another direction of measurement. It is interesting to see!
For the second channel I will attempt to try different CCS - as Peter provided on the board as well as very elaborate Zen Mode's CCS from Babelfish. That will take some creative thinking in order to add the daughter of the daughter's board.
There should be no significant effect on differential DC, which should be stable from cold to hot to within 10mV or so, which is nothing for any speakers. Absolute DC (ref to Gnd) is not so important, and you can allow up to +/-2V with 24V rails. Once you have the entire thing in a housing, there is no stability problems. If you wish, you can put a heatsink on the TO92 to increase thermal mass (I did, to all JFETs).
There is no quieter CCS than a single 2SJ74; If you want current stability instead of low noise, you might as well use a TL431. I know what I shall choose (and I did).
Patrick
There is no quieter CCS than a single 2SJ74; If you want current stability instead of low noise, you might as well use a TL431. I know what I shall choose (and I did).
Patrick
All correct, differential DC is dead on stable, as far as I remember even much lower than 10mV. And absolute DC, again correct, goes widely from when amp is just turned on in my case +/-3.5V to close to zero and than goes little bit up and down based on ambient temp.
Thank you for the advice on TL431. I am more curious than anything else to see and learn other configurations. My whole goal in this is to play and learn with it. Now that I have an opportunity to play, nothing better than understanding what you guys, much more experienced and knowledgeable are talking about. I decided to try all this different amps mostly for the sake of learning, without a serious goal, what makes it really relaxing and exciting for me. And if I end up with better amp, great, but that is really not that important by now. So far it has been a real pleasure.
Thanks
Vladimir
forget about 431 - not enough elegant solution here 
version with two bjt's is more stable temp-wise than with one jfet , and certainly better than 431 , at least for my old ears .....
talking about DC offset drift - induced by temp. variations - be aware that input LTP jfets are same sensitive as jfet CCS ...... so - including other type of CCS will not solve entire "problem"
anyway - as EUVL pointed - once , when you put all that drek in case - when entire system reach temp equilibrium , everything will be OK .
but - I presume - that you already know all that - you made X600 , and these issues are there too , even if smaller in magnitude .
version with two bjt's is more stable temp-wise than with one jfet , and certainly better than 431 , at least for my old ears .....
talking about DC offset drift - induced by temp. variations - be aware that input LTP jfets are same sensitive as jfet CCS ...... so - including other type of CCS will not solve entire "problem"
anyway - as EUVL pointed - once , when you put all that drek in case - when entire system reach temp equilibrium , everything will be OK .
but - I presume - that you already know all that - you made X600 , and these issues are there too , even if smaller in magnitude .
forget about 431 - not enough elegant solution here
version with two bjt's is more stable temp-wise than with one jfet , and certainly better than 431 , at least for my old ears .....
talking about DC offset drift - induced by temp. variations - be aware that input LTP jfets are same sensitive as jfet CCS ...... so - including other type of CCS will not solve entire "problem"
anyway - as EUVL pointed - once , when you put all that drek in case - when entire system reach temp equilibrium , everything will be OK .
but - I presume - that you already know all that - you made X600 , and these issues are there too , even if smaller in magnitude .
Thanx to both of you! Great info.
I just need to point out, that I didn't want to write about problem since I do not see it as a problem, more like just sharing what I have experienced and learned so far regarding this amp.
For sure, no one will be blowing in my jFets once they are closed in
box.
I don't spoil an all-FET design with a BJT .....
Patrick
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hence I have cunnin' plan ......... to revert (silently ) Pass Labs - diyAudio to Tubes / Valves - diyAudio
just imagine all these dead bugs , awaken in all Glowing Glory .......
I know but I asked your opinions
Also, I was specifically intersted in balanced F5, very little written about this and I think very few people have built it.
I don#t have a habit of publishing photos of my projects, but there is a teaser....
Patrick
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Why, there is so much to show? This looks beautiful. What I am finding, circuits and well executed designs like in this picture, are real art forms. Too bad, they ended up boxed in the case.
I could tell, you like small cute heatsinks.
Luke,
some month ago I've build a balanced F5 (Patrick's Xed version), so maybe this two posts from the F5 thread are interesting for you:
post #5659
post #6043
I also have Peter's AJ-X pcbs but unfortunately no time to build one.
Uwe
some month ago I've build a balanced F5 (Patrick's Xed version), so maybe this two posts from the F5 thread are interesting for you:
post #5659
post #6043
I also have Peter's AJ-X pcbs but unfortunately no time to build one.
Uwe